300 BLK accuracy problems? Maybe it isn’t you…

The ability to shoot 30 caliber bullets from a standard AR-15 M16/M4 style rifle by simply changing the barrel and ammunition has made the 300 AAC Blackout (300 BLK) a popular choice for AR shooters looking for an alternative to 223 Remington/5.56 NATO.  Beyond the upgrade in bullet diameter, the 300 BLK offers the versatility of heavy 220 grain plus subsonic projectiles as well as lighter supersonic offerings.  This is certainly the prominent selling point of the cartridge, but one of the areas the 300 BLK will sometimes lack is accuracy.

AR-15/M16 cartridge line up (left to right): 223 Remington/5.56mm NATO, 6.5 PCC virgin brass, 6.5 PCC fire formed brass, 6.5 Grendel, 6.8 SPC, 300 AAC BLK, 7.62x40 WT and 30AR. Note the relatively short (.145") neck on the 6.5 PCC.

AR-15/M16 cartridge line up (left to right): 223 Remington/5.56mm NATO, 6.5 PCC virgin brass, 6.5 PCC fire formed brass, 6.5 Grendel, 6.8 SPC, 300 AAC BLK, 7.62×40 WT and 30AR. Note the relatively short (.145″) neck on the 6.5 PCC.

In my opinion, the bread and butter of the 300 BLK is short barrel rifle applications, especially with a suppressor (what isn’t cool about a 10″ 300 BLK with a can and IR laser?)  Once you start trying to do other things with the 300 BLK, better options emerge.

Take a look at some legitimate load development and testing and you’ll start to notice that it is very hard to get a 300 BLK to shoot consistently well with both a subsonic and supersonic cartridges from the same gun- a fact that has led a few major manufacturers to avoid introducing bolt-action rifles in this caliber.  On some well-known and established forums, you’ll note the majority of load development occurs at short ranges with 50 yards being common and 25 yard groups appearing at times!

My personal experience mirrors this.  Back in 2012, I reviewed the 300 BLK in a 16″ AAC upper with Remington super sonic and subsonic loads, a link to the post can be found here.  The upper functioned flawlessly and accuracy was about 2 MOA, which it turns out, isn’t too shabby for a BLK, but was still less than I had envisioned, especially considering the 7.62x50WT and 30 AR rifles I was testing around the same time shot about 1 MOA (read my 30 AR review here).

300 AAC upper as configured for firing standards. Note the target underneath was used fro accuracy testing with the Leupold Mark 4 scope.

Years later, I headed out the range with a custom Remington Model 7 chambered in 300 BLK. I spent a lot of time (and money) building this rifle.  I even took the time to order a special 1:7″ twist barrel from Bartlein barrel to give me the edge with the heavy loads.

custom 300 BLK model seven 13

The rifle, as pictured above, includes the following parts from Brownells:

It took 26 different loads to get it end up with both a super and subsonic load around a MOA.  It wasn’t the precision love fest I envisioned.  Imagine dumping a pile of money into a rifle and having it shoot some loads nearly 4 MOA!- I was that guy- something I seldon experience during the load development process.  After a number or trips to the range and a lot of brass and bullets, I found a load that would work- note the bughole in the middle left side of the target below.

300 blk target 2

Was I alone in my 300 BLK experience?  Apparently not.  I’ve gotten quite a few emails from shooters with experiences mirroring mine.  Often they’ll ask something like, “I’ve been shooting and reloading for years, no matter what I try, I can’t get the gun to shoot better than 2 MOA, with an occasional 1 MOA group, why is this”?

It may only be me, but when I do encounter a 300 BLK that shoots, it’s often not a true 300 BLK.  SAAMI specifies a 1 in 8″ twist in order to stabilize the heavy loads, most of the uber accurate 300 BLKs you’ll see have a much slower twist to work with the supersonic loads.

So why do I think the 300 BLK isn’t an inherently accurate?  Two reasons, case capacity and barrel twist.

The 300 BLK has such a small case you are effectively loading pistol powder into a rifle cartridge.  This means smaller powder charges and faster powders.  Not the best for accuracy.  In many ways, the 300 BLK in design terms is the opposite of a modern match cartridge like the 6mm BR or 6.5×47 Lapua.

Most barrel makers and benchrest shooters will tell you the best accuracy for a given bullet is obtained with a twist rate that just stabilizes the bullet.   With a bullet that isn’t over stabilized, factors that can be detrimental to accuracy, such as a concentricity issue, can be mitigated.  Frank Green at Bartlein barrels uses the example of High Power rifle competitors using stock Colt 1:7″ rifles back in the day experiencing 4 MOA results with 55 grain loads, and sub MOA with the same rifle and shooter using the 69 SMK.  By utilizing a fast twist to stabilize the long heavy subsonic bullets, I suspect accuracy suffers on the lighter loads.  Keep in mind, that its wildcat predecessors like the .300-221 were known to be fairly accurate with the right twist rate.

I like my 300 BLK, but see it for what it is.  If you are looking for a cartridge that can run with subsonic and supersonic ammunition in your AR, it is a great choice.  If you are looking for an easy to tune, high accuracy round, you may be better served elsewhere.

If you spent a lot of time with your 300 BLK and couldn’t get the precision you wanted out of it, maybe it wasn’t you?

Wish someone told you this before?  Well, someone did.  That person was Bill Wilson of Wilson Combat with his 7.62x40WT.   The cartridge, primarily intended for hunting, offers a greater case capacity and comes with a 1:12″ twist (so you can’t stabilize the heavies).  The 7.62x40WT is a nifty little cartridge for the modern hunter who wants to stalk game with a standard sized AR-15 M16/M4.  Much like the 300 BLK, the 7.62x40WT only requires a new barrel and ammunition to switch calibers.   It is a shame, it never caught on as much as it should have.  To learn more about the 7,62x40WT click here.

Do you have a 300 BLK that hammers (say, five 5 shot groups under 1 MOA in a row)?  Please share the pictures of the groups with us on Facebook and what load you are using, I think there is a lot of interest.

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